Smash Upgrade Options

[BNAL]

I wanted to know if it was possible to utilize the Coleman Regulator in the smash? http://lyrima.co.uk/heatv7pdf/

I’m thinking of getting the Smash and wanted to know what the possibilities are for making changes.

[Paul Birkeland]

You would have to do a bit of redesigning of the circuit since the Coleman Regulator specifies a 7V DC supply for running the 4P1L at 2.1V (it seems a bit lossy).  Doing this will cause you to lose the convenient center tap position for the bias connection.

[BNAL]

I thought the Coleman ran the filament at 8-10v? Does the Smash transformer have enough voltage (14VAC) to run the regulator.

I was also think that I could run a 2P29L tube with some adjustment of the bias.

[Paul Birkeland]

The 4P1L has a 4.2V filament center tapped in the middle, so it needs a DC supply of 2.1 or 4.2V.  The manual for the Coleman filament regulators gives some numbers for heating the 4P1L at 2.1V.

The Smash power transformer does not have a 14V winding.

[mcandmar]

It is recommended to have a supply around 5v higher than the filament voltage, though you can get away with 2-3v with the latest V7 boards.  As Paul says you can run the filaments in parallel or in series, the former having slightly lower distortion.  Google Ali Moglias web site as he has done a lot of testing with 4P1L tubes and Coleman regulators, there is also a ton of information on the DIYAudio forum for the Coleman Regs.